Method of highlighting with a reversible highlighting mixture, highlighting kit, and highlighted complex

ABSTRACT

A highlightable mixture, such as an ink, including a colored pigment, an eradicable colorant, and a non-eradicable colorant; a kit including the highlightable mixture and an eradicator fluid; an colorant complex including a colorless or substantially colorless eradicable dye selected from the group consisting of diarylmethane derivatives, triarylmethane derivatives, and methine dyes, and a colored pigment; and methods of applying an eradicator to at least a portion of a marking made with a highlightable mixture, are described herein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of application Ser. No. 10/956,584 filedon Oct. 1, 2004, which is a continuation-in-part of application Ser. No.10/680,362 filed Oct. 7, 2003 now U.S. Pat. No. 7,083,665, thedisclosures of which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

The invention relates generally to color changing compositions.

2. Brief Description of Related Technology

Eradicable mixture systems, such as inks, generally include twocomponents. One component is an aqueous mixture that includes adye—typically a triarylmethane—that can be rendered substantiallycolorless when contacted with a substance such as a sulfite reducingagent, an amine, or other basic compounds such as hydroxides. The secondcomponent is an aqueous eradicator fluid that includes a complementarysubstance that can cause the dye to convert to a substantially colorlessform. For example, a user writes with an eradicable ink and, ifcorrection is necessary, applies the eradicator fluid to the ink markingto decolorize the dye.

Highlighting a marking is typically performed using a fluorescent inkapplied over a regular marking made by an ink on a substrate (e.g.,paper). A typical fluorescent highlighting ink has a translucent qualityto allow for a user to apply the highlight ink and yet still see theregular ink marking under the fluorescent ink marking made by themarker. While this process serves to highlight a regular ink marking, italso has the undesirable effects, such as highlighting areas of thesubstrate that do not include a regular ink marking.

SUMMARY

One aspect of the disclosure is a method of reversibly highlightingincluding the steps of applying a mixture including water, a pigment,and an eradicable dye to a substrate to make a mark, applying aneradicator fluid to at least a portion of said mark, and applying anoxidizing agent to at least a portion of said mark. Any of such marksare optionally free of volatile solvents.

Another aspect of the disclosure includes a method of highlightingincluding the step of applying an oxidizing agent to an eradicated dyeto produce a visible dye.

Another aspect of the disclosure is a kit including a highlightablemixture described herein, an eradicator fluid, and an oxidizing agent.

Yet another aspect of the disclosure is a complex, including a mixtureof a colored pigment, an eradicable dye, an eradicator fluid, and anoxidizing agent, and optionally the complex is free of volatilesolvents.

Further aspects and advantages of the invention will be apparent tothose skilled in the art from a review of the following detaileddescription, taken in conjunction with the appended claims. While themixture, method of using the mixture, the kit, and the complex aresusceptible of embodiments in various forms, the description hereinafterincludes specific embodiments with the understanding that the disclosureis illustrative, and is not intended to limit the claims to the specificembodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a theoretical mechanism for the conversion of AcidViolet 17 from a violet colored compound to a substantially colorless(eradicated) compound.

FIG. 2 illustrates a theoretical mechanism for the conversion from AcidViolet 17 that has been rendered colorless by a reducing agent to acolored state.

DETAILED DESCRIPTION

The process of ink marking and eradication can proceed in two steps: thefirst is the marking of a substrate (e.g., paper) with an eradicableink, and the second is the application of an eradication solution to themarking. A typical formulation for an eradicable ink includes a solvent(e.g., water) to dissolve a dye that is capable of being eradicated(e.g., a triarylmethane dye). The eradication solution includes aneradicator that, by a chemical process, converts a complementary coloreddye into a substantially colorless compound or a color that matches thatof the substrate (e.g., white for white paper). Such compounds includeoxidizing agents, reducing agents, acid-base reactants, and chemicalsthat can sublime under the influence of heat. Without intending to belimited to any particular method of eradication, it is believed that fortriarylmethane dyes, for example, the active colored dye is able toreflect color in the visible range (between 380 nm to 780 nm) because ofthe conjugation of the aromatic rings in the molecule; however, once areducing agent (e.g., sodium sulfite) is applied to the triarylmethanedye, it destroys the conjugation by converting the sp² carbon center(shown in FIG. 1 with a *) to an sp³ carbon by oxidizing that carboncenter. Once this change in the hybridization takes place, theconjugation between the various rings of the dye molecule is lost andthe dye molecule becomes colorless. This proposed process is shown inFIG. 1 for Acid Violet 17.

The highlightable nature of the ink is derived from the ability toconvert the dye (chromophore) from a colored compound to at leastsubstantially colorless, while not substantially affecting thesubstantially insoluble, colored pigment. As discussed above, this canbe achieved with the combination of a colored pigment and a dye that issensitive to an eradicator (e.g., a reducing agent, a base, heat, etc.).Dyes which are capable of becoming at least substantially colorless uponthe application of an eradicator include diarylmethane derivative dyes,triarylmethane derivative dyes, and methine derivative dyes. Diaryl dyessuitable for use with the inks described herein include Auramine O(Chemical Index No. 41000), and Basic Yellow 2 (Chemical Index No.41000). In the colored state, the bi- and triarylmethane, and methinedyes often contain one or more cationic imine groups. The genericstructure of a triarylmethane dye is shown below in formula (II):

wherein each R group is the same or different and preferably is selectedfrom C₁ to C₁₀ alkyl groups. A non-exhaustive list of triarylmethanedyes for use in inks described herein are listed below in Table I.

TABLE I¹ Color Color Index Name Index No. Common/Commercial Name AcidBlue 22 42755 Water Blue I Acid Blue 93 42780 Methyl Blue Acid Fuchsin42685 Acid Fuchsin Acid Green 42095 Light Green Sf Yellowish Acid Green5 42095 Light Green Sf Yellowish Acid Magenta 42685 Acid Fuchsin AcidRoseine 42685 Acid Fuchsin Acid Rubin 42685 Acid Fuchsin Acid Violet 1742650 Acid Violet 4BN Acid Violet 19 42685 Acid Fuchsin Alizarol CyaninR 43820 Eriochrome Cyanin R Aluminon 43810 Triphenylmethane ChromeViolet Cg Aniline Blue Ws Aniline Blue Ws Basic Blue 8 42563 VictoriaBlue 4r Basic Blue 15 44085 Night Blue Basic Blue 20 42585 Methyl GreenBasic Blue 26 44045 Victoria Blue B Basic Fuchsin Basic Fuchsin BasicGreen 4 42000 Malachite Green Basic Red 9 42500 Pararosanilin Basic Red14 48016 Cationic Brilliant Red 5GN Basic Violet 2 42520 New FuchsinBasic Violet 3 42555 Crystal Violet Basic Violet 4 42600 Ethyl VioletBasic Violet 14 42510 Rosanilin Chrome Violet Cg 43810 TriphenylmethaneChrome Violet Cg Chromoxane Cyanin R 4382 Eriochrome Cyanin R CottonBlue 42780 Methyl Blue Crystal Violet 42555 Crystal Violet Dahlia 42530Hoffman's Violet Diamond Green B 42000 Malachite Green Eriochrome CyaninR 43820 Eriochrome Cyanin R Ethyl Green 42590 Ethyl Green Ethyl Violet42600 Ethyl Violet Fast Green Fcf 42053 Fast Green Fcf Food 3 42053 FastGreen Fcf Gentian Violet Methyl Violet 2b Helvetia Blue 42780 MethylBlue Hoffman's Violet 42530 Hoffman's Violet Light Green 42095 LightGreen Sf Yellowish Lissamine Green Sf 42095 Light Green Sf YellowishMagenta 0 42500 Pararosanilin Magenta I 42510 Rosanilin Magenta IIMagenta II Magenta III 42520 New Fuchsin Malachite Green 42000 MalachiteGreen Methyl Blue 42780 Methyl Blue Methyl Green 42585 Methyl GreenMethyl Violet 42535 Methyl Violet 2b Methyl Violet 2b 42535 MethylViolet 2b Methyl Violet 10b 42555 Crystal Violet Mordant Blue 3 43820Eriochrome Cyanin R Mordant Violet 39 43810 Triphenylmethane ChromeViolet Cg New Fuchsin 4252 New Fuchsin Night Blue 44085 Night BluePararosanilin 42500 Pararosanilin Primula 42530 Hoffman's VioletRosanilin 42510 Rosanilin Solochrome Cyanin R 43820 Eriochrome Cyanin RVictoria Blue 4r 42563 Victoria Blue 4r Victoria Blue B 44045 VictoriaBlue B Victoria Green B 42000 Malachite Green Water Blue I 42755 WaterBlue I ¹See, R. D. Lillie, Conn's Biological Stains (8th ed., 1969),Williams and Wilkins Company, Baltimore, Maryland; Susan Budavari (Ed.),The Merck Index, (12th ed., 1996), Merck & Co., Whitehouse Station, N.J;see also, P. A. Lewis (Ed.), Pigment Handbook Vol. I, Properties andEconomics, sections I(D)f(1) and I(D)g, John Wiley & Sons, (2^(nd) ed.,1988); H. Zollinger, Color Chemistry: Syntheses, Properties, andApplications of OrganicDyes And Pigments, Chapter 4, VCH Publishers(1987); D. R. Waring and G. Hallas (Eds.), The Chemistry and Applicationof Dyes, Chapter 2, Section IX, Plenum Press (1990); and M. Okawara, T.Kitao, T. Hirashima, and M. Matsuoka, Organic Colorants: A Handbook ofData of Selected Dyes for Electro-Optical Applications, Section VI,Elsevier (1988), the disclosures of which are hereby incorporated byreference.

Another type of dye that can be used in an ink are the methine class ofdyes. The methine dyes generally contain one or more methine groupchromophores (—CH═), also called methylidyne or methine group. When themethine dye only contains one methine group the dye is sometimesreferred to as a cyanine dye, with three methine groups the dye issometime referred to as a carbocyanine dye, and with more than threemethine groups the dye is often referred to as a polymethine dye. Anexample of a methine dye is Thiazole Orange:

wherein the bonds that make up the methine group are shown above asbroken lines. Other examples of methine dyes include Basic Red 15, BasicYellow 11, and Basic Yellow 13. For a comprehensive listing of methinedyes, see F. M. Hamer, The Chemistry of Heterocyclic Compounds, A.Weissberger (Ed.), The Cyanine Dyes and Related Compounds, WileyInterscience, New York (1964).

When formulating a highlightable ink of a particular color, whether bythe addition of one eradicable dye or a mixture of eradicable dyes and apigment, the rate of eradication of a dye is a consideration whenselecting an eradicable dye. Without intending to be limited to aparticular mechanism, it is believed that the rate of eradication ofdiarylmethane, triarylmethane, and methine dyes is proportional to theconcentration of the dye in the mixture (e.g., ink or marking made witha mixture). The highlightable ink described herein includes one or moreeradicable dyes selected from the group consisting of diarylmethanedyes, triarylmethane dye, methine dyes, and combinations thereof. In amarking composition, the dye preferably is present in an amount at leastabout 0.01% and up to about 40% by weight of the total weight of themixture, more preferably about 0.1% to about 10% by weight, for exampleup to about 1% by weight or about 1.5% by weight.

In selecting particular dyes and colored pigments for use in the ink,there are a number of dyes and pigments to choose from and, as a result,dyes and pigments of different colors can be mixed to create an ink ofalmost any color. A highlightable ink described herein can include oneor more dyes and one or more pigments that, when combined, provide anink from of a variety of colors. In one embodiment, the dye and pigmentare combined to provide an ink that is black in color in thenon-eradicated state and is red in color in the eradicated (highlighted)state. There are at least two competing considerations when formulatingan ink that includes at least one eradicable dye—the rate of eradicationand the intensity of the color. An increase in the concentration of theeradicable dye used to create the a particular color will increase theintensity of the color, however, as discussed above, an increase in thedye concentration also increases the amount of time needed to eradicatethe dye. It has been found that for the ink described herein a dyeconcentration in an amount at least about 0.1% and up to about 40% byweight based on the total weight of the mixture is a preferredconcentration to balance these considerations.

The ink disclosed herein is can be used on porous or non-poroussubstrates. Nonlimiting examples of non-porous substrates include glass,ceramics, porcelain, plastics, metal, glossy paper and other non-porouspaper such as cardboard or other hardboard material. It has been foundthat the use of a substantially non-soluble pigment in combination withan eradicable dye prevents smearing of the ink upon eradication. Withoutintending to be limited to a particular mechanism for smear reduction,it is believed that when the substantially insoluble pigment is appliedto a porous substrate such as paper, the pigment is not re-dissolved bythe eradicator (e.g., aqueous eradicator) and is further prevented fromsmearing by being disposed in the pores of the substrate and therebyless influenced by the eradicator solution. Alternatively, a similareffect can be achieved with the use of a binder that binds a colorant(e.g., a pigment) to the substrate and, thereby, allows the colorant tobe less influenced by the eradication solution. A preferred ink includesone or more colored pigments, and one or more eradicable dyes.

The eradication solution preferably includes water or an organic solventas the primary solvent, an eradicator such as a sulfite (e.g., sodiumsulfite), bisulfite, or an amine (e.g., sodium glycinate) that can causesusceptible dyes to lose their colors (e.g., triarylmethane dyes) or tochange color, and a film-forming polymer. A suitable eradicator solutionfor the inks described herein is a commercially available eradicatorsolution that includes both a sulfite and an amine as active eradicatingagents (available from Sanford Reynolds of Valence, France).

It has been found, quite surprisingly, that the eradication process canbe made reversible upon the application of an oxidizing agent to theeradicated mixture (or at least a portion of a marking made with themixture and then eradicated). The reversible nature of the eradicationprocess allows for a substantially colorless eradicated dye tosubstantially revert back to its original color. It is expected that thereversal system can be used as a mechanism to correct a highlighting oreradication error such as an unintended eradication of a marking madewith a highlightable and/or eradicable mixture. Without intending to belimited to any particular method of reversing the eradication, it isbelieved that for triarylmethane dyes, for example, the active coloreddye is able to reflect color in the visible range (between 380 nm to 780nm) because of the conjugation of the aromatic rings in the molecule;however, once a reducing agent (e.g., sodium sulfite) is applied to thetriarylmethane dye, it destroys the conjugation by converting the sp²carbon center (shown in FIG. 2 with a *) to an sp³ carbon by oxidizingthat carbon center. Once this change in the hybridization takes place,the conjugation between the various rings of the dye is lost and the dyebecomes at least substantially colorless. It is believed that thereverse of this process occurs when the oxidizing agent acceptselectrons from the sp³ carbon of a substantially colorless dye back to asp² carbon center which is now conjugated with the aromatic rings of thedye and is able to reflect color in the visible range. This proposedprocess is shown in FIG. 2 for Acid Violet 17. For complete reversal ofthe eradication, the oxidizing agent must be able to neutralize anyremaining eradicator left in the mixture (or marking make with themixture).

It has been found that the selection of the eradicator solution for usein a reversible eradication system described herein is selected fromcompounds that can effect this theoretical change from an sp² carboncenter to an sp³ carbon center, and upon the application of an oxidizingagent, revert back to an sp² carbon center. Preferably, the eradicatorfluid includes a reducing agent and is selected from the groupconsisting of a sulfur-containing reducing agent, a basic reducingagent, and combinations thereof. It has also been found that when asulfur-based reducing agent eradicator (e.g., sodium sulfite) is used,the reversibility of the eradication process is particularly facile.Thus, a reducing agent eradicator is preferably used to eradicate aneradicable mixture, more preferably a sulfur-based reducing agent (e.g.,sodium sulfite). Still more preferably, a sulfur-based eradicator isselected from the group consisting of a sulfite reducing agent (e.g.,sodium sulfite), a bisulfite reducing agent, a metasulfite reducingagent, a thiosulfite reducing agent, and combinations thereof.

The reversion of the eradicable dye from its substantially colorlessstate back to its substantially colored state can be performed by theapplication of an oxidizing agent to the mixture that has beeneradicated or to a marking made with a mixture described herein and theneradicated. Oxidizing agents are substances that cause some otherspecies to be oxidized or to lose electrons. For an oxidation process tooccur, the oxidizing agent must undergo reduction and the relativeoxidizing and reducing strengths of the oxidizing agent and thecolorless dye can be used to predict whether or not the oxidation islikely to occur on an given species. For an eradicable dye used hereinthe agent to be reduced (i.e., lose electrons) is an sp³ carbocation. Aexample of one such carbocation is the eradicated Acid Violet 17 shownbelow (the sp³ carbocation is labeled with a “*”):

To completely effect the reversal of the eradication, any remainingeradicator in the mixture (or marking make with the mixture) should beneutralized by the oxidizing agent. Thus, the oxidizing agent used inthe reversible eradication described herein has a reduction potentialthat, when compared to the reduction potential for the eradicator,yields a net negative Gibb's free energy (ΔG). The acid oxidizing agentcan be a strong acid or weak acid, or a combination thereof. The acidoxidizing agent can also be selected from the group consisting ofmonobasic acids, di-basic acids, tri-basic acids, tetra-basic acids, andcombinations thereof. Preferably, the oxidizing agent used is an acidand is selected from the group consisting of mineral acids, organicacids, and combinations thereof. Preferably, the mineral acids areselected from the group consisting of hydrochloric acid, hydrobromicacid, hydroiodic acid, hydrofluoric acid, nitric acid, sulfuric acid,carbonic acid, chromic acid, phosphoric acid, phosphorous acid,phosphonic acid, and combinations thereof. Preferably, the organic acidsare selected from the group consisting of benzoic acid, lactic acid,acetic acid, propanoic acid, acetoacetic acid, crotonic acid, formicacid, glycolic acid, glyoxylic acid, lactic acid, pyruvic acid,trans-aconitic acid, fumaric acid, maleic acid, malic acid, tartaricacid, acetylenedicarboxylic acid, tetrahydrophthalic acid, mesaconicacid, phthalic acid, isophthalic acid, terephthalic acid, itaconic acid,transethyleneoxidedicarboxylic acid, succinic acid, adipic acid,pimellic acid, suberic acid, azelic acid, substituted phosphoric acid,substituted phosphorous, citric acid, hemimellitic acid, trimellitic,trimesic acid, 2-carboxyethyliminodiacetic acid, nitrilotriacetic acid,phosphonic acid, substituted phosphonic acid, mellophanic acid,prehnitic acid, pyromellitic acid, 2-phosphonoethyliminodiacetic acid,diethylenetetraacetic acids, and combinations thereof. The oxidizingagent is preferably miscible or soluble in water, and the oxidizingagent is preferably an aqueous mixture.

It has also been found that the eradication can be reversed with theaddition of a strongly nucleophilic species. Without intending to belimited to a particular mechanism, it is believed that a stronglynucleophilic species is attracted to the carbocation of the eradicateddye, and this attraction leads to the attack by the nucleophilic specieson the carbocation and the formation of a re-conjugated colorederadicable dye. Thus, an eradicable reaction described herein ispreferably reversed by the application of a nucleophile to theeradicable mixture or a marking made with the eradicable mixture, morepreferably the nucleophile is an alkoxide.

The process of reversibly highlighting with an ink begins with theeradication of the eradicable dye(s) in the ink mixture with aneradicator. The colored pigment, however, is substantially unaffected bythe eradicator and continues to contribute to the color of the ink. Ahighlightable ink described herein can have three different coloredstates. The first state can be described as the non-eradicated state,wherein the ink (or at least a portion of a marking made with the ink)has not come in contact with an eradicator. A second state of color canbe described as the eradicated (highlighted) state, wherein the ink (orat least a portion of a marking made with the ink) has come in contactwith the an eradicator and the ink has made a change in color,preferably sufficient to be perceptible to the human eye. A third stateof color can be described as the reversed state of color, wherein thecolor of the mixture (or mark) includes contributions from a pigment andthe eradicable dye that has been converted from substantially colorlessto substantially back to its original non-eradicated color. Uponcomplete reversal, the third state of color is the same as or visuallyindistinguishable from the first state. Once the dye is eradicated (theeradicable dye is in the eradicated state), the color of the inkpreferably is primarily determined by the color contributed by thecolored pigments in the ink mixture. It is preferred that the colorcontributed by the color pigments is different from the color of the inkin its non-eradicated state, to achieve drastic highlighting andreversal effects that are at least noticeable to human eye. Preferably,the color of the ink in its non-eradicated state is black, and the colorof the ink in the eradicated state is either red, green, or blue.

Pigments for use in the ink described herein cover a wide variety ofcolors and types, including organic, inorganic, natural, and syntheticpigments. Preferred pigments are substantially insoluble in an aqueousmedium and are particulate material that is dispersed in the inksolution. Typically, pigments are chemically inert, non-toxic, andstable to heat and light. A non-exhaustive list of pigment for use ininks described herein are listed below in Table II.

TABLE II Color Index Pigment Common/Commercial Name Manufacturer HuePermanent Yellow DHG Hoechst Yellow 12 (Frankfurt, Germany) PermanentYellow GR Hoechst Yellow 13 (Frankfurt, Germany) Permanent Yellow GHoechst Yellow 14 (Frankfurt, Germany) Permanent Yellow NCG-71 HoechstYellow 16 (Frankfurt, Germany) Permanent Yellow GG Hoechst Yellow 17(Frankfurt, Germany) Hansa Yellow RA Hoechst Yellow 73 (Frankfurt,Germany) Hansa Brilliant Yellow 5GX-02 Hoechst Yellow 74 (Frankfurt,Germany) DALAMAR Yellow YT-858-D Heubach Yellow 74 (Langelsheim,Germany) Hansa Yellow X Hoechst Yellow 75 (Frankfurt, Germany) NOVOPERMYellow HR Hoechst Yellow 83 (Frankfurt, Germany) CHROMOPHTAL Yellow 3GCiba-Geigy Yellow 93 (Basle, Switzerland) CHROMOPHTAL Yellow GRCiba-Geigy Yellow 95 (Basle, Switzerland) NOVOPERM Yellow FGL HoechstYellow 97 (Frankfurt, Germany) Hansa Brilliant Yellow 10GX HoechstYellow 98 (Frankfurt, Germany) Permanent Yellow G3R-01 Hoechst Yellow114 (Frankfurt, Germany) CHROMOPHTAL Yellow 8G Ciba-Geigy Yellow 128(Basle, Switzerland) IRGAZIN Yellow 5GT Ciba-Geigy Yellow 129 (Basle,Switzerland) HOSTAPERM Yellow H4G Hoechst Yellow 151 (Frankfurt,Germany) HOSTAPERM Yellow H3G Hoechst Yellow 154 (Frankfurt, Germany)L74-1357 Yellow Sun Chemical (Cincinnati, Ohio) L75-1331 Yellow SunChemical (Cincinnati, Ohio) L75-2377 Yellow Sun Chemical (Cincinnati,Ohio) HOSTAPERM Orange GR Hoechst Orange 43 (Frankfurt, Germany)PALIOGEN Orange BASF Orange 51 (Mount Olive, New Jersey) IRGALITE Rubine4BL Ciba-Geigy Red 57:1 (Basle, Switzerland) QUINDO Magenta MobayChemical Red 122 (Haledon, New Jersey) INDOFAST Brilliant Scarlet MobayChemical Red 123 (Haledon, New Jersey) HOSTAPERM Scarlet GO Hoechst Red168 (Frankfurt, Germany) Permanent Rubine F6B Hoechst Red 184(Frankfurt, Germany) MONASTRAL Magenta Ciba-Geigy Red 202 (Basle,Switzerland) MONASTRAL Scarlet Ciba-Geigy Red 207 (Basle, Switzerland)HELIOGEN Blue L 6901F BASF Blue 15:2 (Mount Olive, New Jersey) HELIOGENBlue NBD 7010 BASF (Mount Olive, New Jersey) HELIOGEN Blue K 7090 BASFBlue 15:3 (Mount Olive, New Jersey) HELIOGEN Blue L 7101F BASF Blue 15:4(Mount Olive, New Jersey) PALIOGEN Blue L 6470 BASF Blue 60 (MountOlive, New Jersey) HEUCOPHTHAL Blue G, XBT-583D Heubach Blue 15:3(Langelsheim, Germany) HELIOGEN Green K 8683 BASF Green 7 (Mount Olive,New Jersey) HELIOGEN Green L 9140 BASF Green 36 (Mount Olive, NewJersey) MONASTRAL Violet R Ciba-Geigy Violet 19 (Basle, Switzerland)MONASTRAL Red B Ciba-Geigy Violet 19 (Basle, Switzerland) QUINDO RedR6700 Mobay Chemical (Haledon, New Jersey) QUINDO Red R6713 MobayChemical (Haledon, New Jersey) INDOFAST Violet Mobay Chemical Violet 23(Haledon, New Jersey) MONASTRAL Violet Maroon B Ciba-Geigy Violet 42(Basle, Switzerland) RAVEN 1170 Columbian Chemicals Black 7 (Marietta,Georgia) Special Black 4A Degussa Black 7 (Parsippany, New Jersey)STERLING NS Black Eastech Chemical, Inc. Black 7 (Philadelphia,Pennsylvania) STERLING NSX 76 Eastech Chemical, Inc. Black 7(Philadelphia, Pennsylvania) TIPURE R-101 Du Pont, (Wilmington,Delaware) Mogul L Eastech Chemical, Inc. Black 7 (Philadelphia,Pennsylvania)

To prepare an ink of a particular color, the amount of colored pigmentused in an ink can be balanced with the amount of dye present in the inkto produce the desired color of the ink in its non-eradicated state.Also, when a large amount of colored pigment is used, depending on thesubstrate, the pigment may over saturate the substrate once the solvent(e.g., water) has evaporated. If over-saturation occurs, the applicationof the eradicator fluid to the marking can cause smearing of the pigmenton the surface of the substrate. Thus, the ink preferably contains aneffective amount to prevent smearing upon application of the eradicatorsolution, when the smearing effect is not desired. The colored pigmentpreferably is present in an amount at least about 0.01% and up to about50% by weight of the total weight of the mixture, more preferably atleast about 0.1% and up to about 20% by weight, for example up to about3.5%, 7%, or 10% by weight.

The color of the ink will primarily be determined by the combination ofan eradicable dye and a colored pigment which causes the ink to reflecta particular wavelength of visible light. The mixture of a dye andpigment of different colors can form an ink mixture in a wide variety ofcolors. The color selection can be done with the use varying amounts oftwo or more complementary colors, or combinations that contain all threeprimary colors (red, yellow, and blue). When two complementary colorsare mixed, the resultant mixture is gray, with black being thecompletely saturated form of gray. The complement color of red is green,the complement color of orange is blue, and the complement color ofyellow is violet. When using complementary colors, these pairs ofcomplementary colors actually reflect all three primary colors. Forexample, when red and green dyes are mixed as complementary colors, itis the equivalent of mixing red with yellow and blue, because green iscomposed of a mixture of the two primary colors yellow and blue. Inanother example, the mixture of the two complementary colors yellow andviolet is the equivalent of mixing yellow with red and blue, becauseviolet is composed of two primary colors, red and blue.

An ink described herein can optionally include a binder resin to impartsmear resistance and water resistance to the ink. Binder resins for usein the ink preferably include glycols such as polyethylene glycol,polyvinylpyrrolidone and copolymers and salts thereof, polyvinylacetateand copolymers and salts thereof, and polyacrylic acids and copolymersand salts thereof, other film-forming, water-soluble resins, andcombinations of the foregoing. The binder resin preferably is selectedfrom PVP and copolymers thereof, PVA and copolymers thereof, andcombinations of the foregoing. More preferably, the binder resin isselected from PVP, copolymers thereof, and combinations of theforegoing.

The binder resin can also be used to control the viscosity of the ink.When a highly viscous ink is desired (e.g., cP>10,000), the use of alarger amount a binder resin will achieve a highly viscous ink. When thebinder resin used is a polymer (e.g., PVP), the resin can be selectedwith a wide range of viscosities and molecular weights. For example, PVPis commercially available at various viscosities, and in a molecularweight range of 10,000 daltons to 1,300,000 daltons (Aldrich ChemicalCo., Inc., Milwaukee, Wis.) for example. Thus, depending on themolecular weight of the polymer resin, there can be a great deal ofvariation in the amount of resin utilized in the ink, and the overallviscosity of the ink. When, for example, a low molecular weight PVP isused, the ink can achieve smear and water resistance while stillmaintaining a low viscosity (e.g., about 2 cP to about 5 cP). A binderresin used herein preferably is present in an amount in a range of about1 wt. % to about 80 wt. % based on the total weight of the mixture, morepreferably about 5 wt. % to about 20 wt. %.

The ink preferably is an aqueous mixutre. Water preferably is present inan amount in a range of about 50% to about 95% by weight of the totalweight of the mixture, more preferably about 60% to about 80% by weight.The water acts to dissolve the dye component and as a medium in which tosuspend the colored pigment and also provides an improved washability ofthe ink from various materials (e.g., clothes) as compared to oil-basedinks.

When an aqueous ink is used in a delivery system such as a writinginstrument or an ink-jet cartridge, is it preferred to use one or moreorganic solvents to control the amount of time it takes for the ink todry once it is applied to a substrate (drying time). Preferred deliverysystems include a writing instrument and an ink-jet cartridge. Ascompared to water, organic solvents will typically evaporate faster thanwater, and when an aqueous ink includes an organic solvent, the dryingtime will decrease. In order to optimize and exercise control over thedrying time of an ink, it may be necessary to include more than oneorganic solvent. An organic solvent preferably is substantially solublein water. Preferably, the organic solvent is selected from the groupconsisting of glycols, ureas, fatty alcohols, dimethylformamide,formamide, dimethylsulfoxide, high molecular weight hydrocarbons (i.e.,a hydrocarbon with twelve or more carbon atoms), low molecular weighthydrocarbons (i.e., a hydrocarbon with eleven or fewer carbon atoms),and combinations thereof. More preferably, the organic solvent ispolyethylene glycol. The organic solvent, when used, preferably ispresent in the ink at least about 5% and up to about 30% by weight basedon the total weight of the mixture, more preferably at least about 10%and up to about 20% by weight, to achieve a drying time suitable fortypical writing instruments and marking applications.

Glycols for use as an organic solvent include, but are not limited to,three broad categories of glycols: (a) glycol ethers (e.g., ethyleneglycol monomethyl ether, ethylene glycol monoethyl ether, ethyleneglycol monobutyl ether, ethylene glycol monophenyl ether, diethyleneglycol monomethyl ether, diethylene glycol monoethyl ether, diethyleneglycol monoisopropyl ether, diethylene glycol monobutyl ether,diethylene glycol monophenyl ether, ethylene glycol dimethyl ether,ethylene glycol diethyl ether, diethylene glycol dimethyl ether,propylene glycol monomethyl ether); (b) glycol ether acetates (e.g.,ethylene glycol monomethyl ether acetate, ethylene glycol monoethylether acetate, ethylene glycol monobutyl ether acetate, ethylene glycolmonophenyl ether acetate, diethylene glycol monomethyl ether acetate,diethylene glycol monoethyl ether acetate, diethylene glycol monobutylether acetate, diethylene glycol monophenyl ether acetate, diethyleneglycol monoisopropyl ether acetate, ethylene glycol dimethyl etheracetate, ethylene glycol diethyl ether acetate, diethylene glycoldimethyl ether acetate, propylene glycol monomethyl ether acetate, andthe like); and (c) glycol acetates (e.g., ethylene glycol monoacetate,ethylene glycol diacetate, and diethylene glycol diacetate). In otherembodiments, the ink can include other glycols not within one of thesethree categories, including glycols such as ethylene glycol, andethoxylated glycols. A glycol can be used in the ink compositionpreferably in an amount in the range of about 10% to about 20% by weightbased on the total weight of the mixture.

Fatty alcohols for use as an organic solvent include, but are notlimited to, alcohols having eight through twenty carbon atoms, and fattyalcohols that are ethoxylated with one to three molar equivalents ofethylene oxide. Examples of fatty alcohols and ethoxylated fattyalcohols include, but are not limited to, behenyl alcohol, caprylicalcohol, cetyl alcohol, cetaryl alcohol, decyl alcohol, lauryl alcohol,isocetyl alcohol, myristyl alcohol, oleyl alcohol, stearyl alcohol,tallow alcohol, steareth-2, ceteth-1, cetearth-3, and laureth-2.Additional suitable fatty alcohols are listed in CTFA CosmeticIngredient Handbook, First ed., J. Nikotakis (Ed.), The Cosmetic,Toiletry and Fragrance Association, pages 28 and 45 (1988), incorporatedherein by reference.

A mixture described herein can include one or more humectants todecrease or increase the drying time or cap-off time of an ink describedherein (e.g., when the mixture is disposed in a writing instrument orink-jet application). Without intending to be limited to a particularmechanism of altering the drying time, it is believed that a humectant,which is typically an organic solvent, added to the ink contributes tothe volatility of the ink mixture such that the humectant eitherincreases or decreases the volatility of the ink, and thereby decreasesthe drying time (i.e., when the mixture is applied to a substrate)and/or increase the cap-off time (i.e., when the mixture is disposed ina delivery device such as a writing instrument). Preferably, for anaqueous mixture described herein a humectant is selected such that it ismiscible with water, and more preferably is an organic solvent that ismiscible with water. Preferably, a volatile organic solvent is selectedfrom the group consisting of polyethylene glycol, ethylene glycol,propylene glycol, diethylene glycols, glycerine, dipropylene glycols,polypropylene glycols, amides, urea, substituted ureas, ethers,carboxylic acids, esters, alcohols, organosulfides, organosulfoxides,sulfones, alcohol derivatives, carbitol, butyl carbitol, etherderivatives, amino alcohols, ketones, N-methylpyrrolidinone,2-pyrrolidinone, cyclohexylpyrrolidone, hydroxyethers, amides,sulfoxides, lactones, and combinations thereof.

Preferably, the ratio of water in a mixture to organic in the mixture(e.g., organic solvent and/or humectant) is in a range of about 100:0 toabout 30:70 by weight based on the total weight of the mixture, morepreferably from about 97:3 to about 50:50.

For a liquid to effectively wet and spread out on a surface (e.g.,paper), the surface tension of the liquid must be less than the surfacetension of the surface. An organic solvent can also be selected to alterthe surface tension of the mixture to create a mixture that has enoughsurface tension to wet a variety of surfaces. The mixture preferablyincludes a glycol to alter the surface tension of the mixture, morepreferably polyethylene glycol.

In the ink described herein, the color green can be achieved by themixing of the combination of dyes and pigments of either twocomplementary colors (e.g., green-red, or yellow-magenta) or bydyes/pigments with the combination of all three primary colors (red,yellow, and blue). A dark green ink is preferably formed from thecombination of a green dye with a pigment selected from the groupconsisting of a red pigment, a violet pigment, and combinations thereof.A preferred combination is a green dye and red pigment, and thepreferred combination is Basic Green 4 and a red pigment or acombination of pigments that combine to form a red pigment dispersion.The preferred red pigment dispersion is LUCONYL 3855 available from BASFof Charlotte, N.C.

When combining two or more colors to form an ink of a desired color, itis understood that the desired color (e.g., black), may be reached eventhough an undertone of another color (e.g., a redish color) might beperceptible. For example, it is understood that an ink that is coloredblack can have a red or a green undertone, and yet still be considered ablack ink.

It has been found that the combination of a green eradicable dye and aviolet and/or a red dye is able to mix to form a green highlightableink. One embodiment of an ink described herein is a green highlightableink, including a mixture of one or more of a colored pigment and one ormore dyes selected from the group consisting of diarylmethanederivatives, triarylmethane derivatives, methine dyes, and combinationsthereof, wherein the mixture of dye and pigment appears green in color.

A green eradicable dye preferably is selected from the group consistingof Acid Green, Acid Green 5, Basic Green 4, Diamond Green B, EthylGreen, Fast Green Fcf, Food Green 3, Light Green, Lissamine Green Sf,Malachite Green, Methyl Green, Victoria Green B, and combinationsthereof, more preferably, the green dye is selected from Basic Green 3,Basic Green 4, and combinations thereof. Preferably, a red dye isselected from the group consisting of Basic Red 9, Basic Red 14, BasicRed 15, Basic Red 29, Basic Red 46, and combinations thereof.Preferably, a violet dye is selected from the group consisting of AcidViolet 17, Acid Violet 19, Basic Violet 2, Basic Violet 3, Basic Violet4, Basic Violet 14, Chrome Violet Cg, Crystal Violet, Ethyl Violet,Gentian Violet, Hoffman's Violet, Methyl Violet, Methyl Violet 2b,Methyl Violet 10b, Mordant Violet 39, and combinations thereof. To forma yellow ink, a yellow dye is preferably selected from the groupconsisting of Basic Yellow 11, Basic Yellow 13, Basic Yellow 21, BasicYellow 28, Basic Yellow 29, Basic Yellow 40, Basic Yellow 49, BasicYellow 291, and combinations thereof.

Preferably a mixture described herein is black in color. It has beenfound, quite surprisingly, that the addition of one or morenon-eradicable dyes to the mixture including a pigment and an eradicabledye improves the richness of the black color in a black highlightablecomposition and improves the contrast between the non-highlightedmixture and the highlighted mixture. Accordingly, a mixture describedherein preferably includes a non-eradicable dye.

It has been found that the addition of a blue, red, violet, yellow,and/or orange non-eradicable dye improves the richness of the blackcolor in a black mixture described herein. Thus, in one embodiment anon-eradicable dye is present in a mixture described herein and ispreferably selected from blue non-eradicable dyes, red non-eradicabledyes, violet non-eradicable dyes, yellow non-eradicable dyes, orangenon-eradicable dyes, and combinations of the foregoing. Preferably, ablue non-eradicable dye is selected from the group consisting of AcidBlue 1, Acid Blue 104, Acid Blue 182, Acid Blue 204, Acid Blue 74, AcidBlue 9, Acid Blue 90, Basic Blue 1, Basic Blue 7, Basic Blue 9, BasicBlue 33, Direct Blue 199, Direct Blue 281, Disperse Blue 73, ReactiveBlue 19, Reactive Blue 21, and combinations thereof. Preferably, a rednon-eradicable dye is selected from the group consisting of Acid Red 18,Acid Red 249, Acid Red 52, Acid Red 87, Acid Red 92, Basic Red 22, BasicRed 28, Basic Red 46, Direct Red 236, Direct Red 252, and combinationsthereof. Preferably, a violet non-eradicable dye is selected from thegroup consisting of Acid Violet 12, Acid Violet 126, Acid Violet 17,Acid Violet 49, Basic Violet 1, Basic Violet 10, Basic Violet 3, andcombinations thereof. Preferably, a yellow non-eradicable dye isselected from the group consisting of Acid Yellow 17, Acid Yellow 118,Acid Yellow 23, Acid Yellow 3, Acid Yellow 32, Acid Yellow 36, BasicYellow 21, Basic Yellow 28, Basic Yellow 37, Basic Yellow 40, BasicYellow 49, Basic Yellow 291, and combinations thereof. Preferably, anorange non-eradicable dye is selected from the group consisting of AcidOrange 10, Reactive Orange 16, and combinations thereof.

One embodiment of the mixtures, methods, and kits described herein is amethod of reversibly highlighting, including the steps of applying amixture comprising water, a colored pigment, and an eradicable dyeselected from the group consisting of diarylmethane derivatives,triarylmethane derivatives, methine dyes, and combinations thereof to asubstrate to make a mark, applying an eradicator fluid to the mark, andapplying an oxidizing agent to the mark.

Also contemplated is a kit including a mixture including water, acolored pigment, and an eradicable dye selected from the groupconsisting of diarylmethane derivatives, triarylmethane derivatives,methine dyes, and combinations thereof, an eradicator solution, and anoxidizing agent. Each of the mixture, eradicator fluid, and oxidizingagent can be disposed in a writing instrument (e.g., a pen) for ease ofuse or it may be supplied in another applicator form such as a dauber, abottled free ink solution, a stamp pad, and the like. Preferably, amixture described herein is disposed in a writing instrument and thewriting instrument is, for example, a ball-point pen, an extrudedplastic porous tip pen, or a marker.

In one application, after a highlightable ink mixture described hereinis applied to a substrate, the volatile solvent(s) present in themixture (e.g., water) will at least substantially evaporate. Uponeradication, the volatile solvent(s) present in the eradicator fluid(e.g., water) will at least substantially evaporate after the eradicatorhas been applied to the mixture. Likewise, when an oxidizing agentpresent in a solvent is applied to the mixture or marking madetherewith, the volatile solvent(s) present in the oxidizing agent willevaporate, thus, leaving the eradication agent (e.g., sulfite,bisulfite) along with the mixture components (e.g., colored eradicabledye and colored pigment), and the oxidizing agent. Thus, another aspectof the invention is a colored complex of the mixture described hereinwith an eradicator fluid and oxidizing agent after the volatilesolvent(s) have substantially or completely evaporated. The highlightedcomplex includes a colored (i.e., substantially non-eradicated)eradicable dye selected from the group consisting of diarylmethanederivatives, triarylmethane derivatives, methine dyes, and combinationsthereof, a colored pigment, an eradicator (e.g., a reducing agent), anoxidizing agent (e.g., a mineral and/or organic acid), and any optionaladditives described herein. In other useful embodiments, the agentsand/or mixtures described herein may be combined in the presence of areaction medium (e.g., a solvent) under conditions in which the medium(e.g., a solvent) is not fugative (e.g., does not evaporate).

The highlighting or color-changing effect of a mixture described hereinin best achieved when the color of the pigment present in the mixture issubstantially unaffected by an eradication solution. Where the color ofthe pigment is substantially unaffected by the eradication solution, thecolor of the pigment contributes to the overall color of the complexcreated by the mixture of eradicated dye, pigment, and eradicationsolution that is created when the eradication solution is applied to themixture. Thus, preferably the color of the colored pigment present in amixture described herein is substantially unaffected by one or more of areducing agent, an oxidizing agent, and a change in pH of the mixture.

A mixture described herein can be used as an ink to make markings on avariety of substrates (e.g., paper). In an ink, a surfactant can be usedto improve the absorption of an ink by a substrate (e.g., paper), and afilm-forming agent can be used to improve the adhesion of the resultingmark to the substrate. Thus, the mixture described herein can includeone or more additives selected from the group consisting of pH buffers,surfactants, biocides, anti-corrosive agents, sequestering agents,anti-crusting agents, rehology control agents, binder resins,film-forming agents, and combinations thereof, in the amounts andproportions conventionally used in inks for various applications.

A mixture described herein can be used in a delivery system such as inan ink-jet application. The mixture can be used in a home-office ink-jetsystem (e.g., a HEWLETT-PACKARD ink-jet printer cartridge), and incommercial and industrial ink-jet applications. Ink-jet printers for usewith a mixture described herein include those that use the continuousinkjet printer technology, which deflects and controls a continuousinkjet droplet stream direction onto the printed media or into a gutterfor recirculation by applying an electric field to previously chargedinkjet droplets, and those that use the drop-on-demand inkjet technology(e.g., piezoelectric and thermal ink-jet printhead), which ejects inkdroplets only when they are needed to print on the media. Preferreddelivery systems include the piezoelectric ink-jet printheads andthermal ink-jet printheads.

A mixture described herein can be used in a number of applications,including those that do not involve the application of the mixture ontoa substrate (e.g., as an ink). Thus, a mixture described herein can beused with or without a substrate serving as a situs of the highlightingor color-changing effect. For example, the mixture described hereincould be used in an application wherein the mixture and an eradicationsolution mix in the liquid phase to create a color change to the mixturewhen the eradication solution contacts the mixture. In another example,the aqueous mixture described herein can be combined in the liquid phasewith an non-aqueous eradicator solution that creates a biphasic mixturewherein the highlighting or color-changing effect of the mixture occursat the biphasic interface of the two solutions.

EXAMPLES

The following examples are provided to illustrate the invention but isnot intended to limit the scope of the invention.

Example 1

A highlightable ink was prepared with the ingredients identified belowin the amounts shown in Table III:

TABLE III Component Function Amount (wt. %) Water Solvent 76.48Propylene Glycol Organic Solvent 19.12 Basic Green 4 Dye 0.96 LUCONYL3855 Pigment 3.44

The propylene glycol (available from EM Science of Gibbstown, N.J.), wasadded at room temperature to the water and mixed until a homogenous,particulate-free solution was formed. The Basic Green 4 dye was thenadded to this solution and the solution was mixed until the dye werefully dissolved. The pigment was then added and the solution was mixedfor an hour until a homogenous solution was formed.

The resulting ink was then put into a SHARPIE marker and applied to asheet of white paper to determine the color of the ink once applied tothe substrate. The ink was observed to be a dark green color.

As described above, it is believed that the major contributing factor tothe length of time it takes to highlight an ink described herein isproportional to the weight percent of eradicable dye present in the ink.Thus, after the ink was applied to a white sheet of paper, theeradication time was tested with a commercially available eradicatorsolution available from Sanford Reynolds of Valence, France. Upon theapplication of the eradication solution to the marking, the markingchanged in color from a dark green to a red, and this conversion tookapproximately five seconds.

Example 2

Two highlightable ink mixtures were prepared with the ingredientsidentified below in the amounts shown in Table IV:

TABLE IV Amount (wt. %) Amount (wt. %) Component Function Formulation 1Formulation 2 Deionized Water Solvent 66.15 64.1 Propylene GlycolOrganic 20.00 20.00 Solvent SPECTRAZINE Non- 0.35 0.50 Yellow GRL 200%Eradicable Dye SPECTRAZINE Non- 3.00 Brilliant Blue Eradicable DyeSPECTRA Soluble Eradicable 1.50 Blue 2B EX Dye SPECTRACID BlackEradicable 6.00 Dye HOSTAFINE RED Pigment 7.50 HF3S HOSTAFINE Pigment10.00 GREEN GN Sodium Acetate Salt 0.90

The propylene glycol (available from EM Science of Gibbstown, N.J.), wasadded at room temperature to the water and mixed until a homogenous,particulate-free solution was formed. The eradicable dyes (SPECTRACIDBlack (available from Spectra Colors Corporation, Kearny, N.J.) toFormulation 1 and SPECTRA Soluble Blue 2B EX (available from SpectraColors Corporation, Kearny, N.J.) to Formulation 2) and non-eradicabledyes (SPECTRAZINE Yellow GRL 200%, Colour Index No. Basic Yellow 291(available from Spectra Colors Corporation, Kearny, N.J.) toFormulations 1 and 2, and SPECTRAZINE Bril. Blue, Colour Index No. BasicBlue 1 (available from Spectra Colors Corporation, Kearny, N.J.) toFormulation 2) were then added to this solution and the solution wasmixed until the dyes were fully dissolved. The pigments (HOSTAFINE REDHF3S, Colour Index No. Pigment Red 188 (available from ClariantCorporation, Coventry, R.I.) to Formulation 1 and HOSTAFINE GREEN GN,Colour Index No. Pigment Green 7 (available from Clariant Corporation,Coventry, R.I.) to Formulation 2) were then added and the solution wasmixed for an hour until a homogenous solution was formed.

The resulting inks were then put into SHARPIE markers and applied to asheet of white paper to determine the color of the ink once applied tothe substrate. The markings resulting from the application offormulations 1 and 2 were observed as a rich black in color. Theresulting markings on white paper where then treated with a commerciallyavailable eradicator solution available from Sanford Reynolds ofValence, France. The markings made with Formulation 1 changed color fromblack to red, and the marking made with Formulation 2 changed color fromblack to green. The eradication of the markings made with bothformulations 1 and 2 did not result in smearing of the marking and onlythe marking made with the ink (e.g., words written on paper) changedcolor (i.e., showed a highlighting effect).

Example 3

Mixtures that include an acid oxidizing agent were prepared by mixingthe materials listed in Table V until a homogenous mixture was formed:

TABLE V Component Function Amount (wt. %) Water Solvent 95 Phosphoricacids Acid/Oxidizing Agent 5 (75%)

The resulting aqueous mixture was placed in a POCKET ACCENT marker andapplied to a marking made and eradicated as described in Example 1. Theapplication of this aqueous acid mixture to the eradicated markingconverted the red eradicated marking back to a dark green color thatappears to the human eye to be identical to the color of thenon-eradicated mixture prepared in Example 1. The reversal of color fromred to dark green (apparently black) took approximately five seconds.

Example 4

Mixtures that include an acid oxidizing agent were prepared by mixingthe materials listed in Table VI until a homogenous mixture was formed:

TABLE VI Component Function Amount (wt. %) Water Solvent 95 Citric AcidAcid/Oxidizing Agent 5

The resulting aqueous mixture was placed in a POCKET ACCENT marker andapplied to a marking made and eradicated as described in Example 1. Theapplication of this aqueous acid mixture to the eradicated markingconverted the red eradicated marking back to a dark green color thatappears to the human eye to be identical to the color of thenon-eradicated mixture prepared in Example 1. The reversal of color fromred to dark green (apparently black) took approximately five seconds.

Example 5

Mixtures that include an acid oxidizing agent were prepared by mixingthe materials listed in Table VII until a homogenous mixture was formed:

TABLE VII Component Function Amount (wt. %) Water Solvent 85 Citric AcidAcid/Oxidizing Agent 10 Phosphoric acids Acid/Oxidizing Agent 5 (75%)

The resulting aqueous mixture was placed in a POCKET ACCENT marker andapplied to a marking made and eradicated as described in Example 1. Theapplication of this aqueous acid mixture to the eradicated markingconverted the red eradicated marking back to a dark green color thatappears to the human eye to be identical to the color of thenon-eradicated mixture prepared in Example 1. The reversal of color fromred to dark green (apparently black) took approximately five seconds.

The foregoing description is given for clearness of understanding only,and no unnecessary limitations should be understood therefrom, asmodifications within the scope of the invention may be apparent to thosehaving ordinary skill in the art. Throughout the specification, wherecompositions are described as including components or materials, it iscontemplated that the compositions can also consist essentially of, orconsist of, any combination of the recited components or materials,unless stated otherwise.

1. A method of reversibly highlighting, comprising the steps of applyinga mixture comprising water, a colored pigment, and an eradicable dyeselected from the group consisting of diarylmethane derivatives,triarylmethane derivatives, methine dyes, and combinations thereof to asubstrate to make a mark, applying an eradicator fluid to said mark, andapplying an oxidizing agent to said mark.
 2. The method of claim 1,wherein said eradicator fluid comprises a reducing agent.
 3. The methodof claim 2, wherein said reducing agent is selected from the groupconsisting of a sulfur-containing reducing agent, a basic reducingagent, and combinations thereof.
 4. The method of claim 3, wherein saidsulfur-containing reducing agent is selected from the group consistingof a sulfite reducing agent, a bisulfite reducing agent, a metasulfitereducing agent, a thiosulfite reducing agent, and combinations thereof.5. The method of claim 1, wherein said oxidizing agent comprises anacid.
 6. The method of claim 5, wherein said acid is selected from thegroup consisting of mineral acids, organic acids, and combinationsthereof.
 7. The method of claim 6, wherein said mineral acids areselected from the group consisting of hydrochloric acid, hydrobromicacid, hydroiodic acid, hydrofluoric acid, nitric acid, sulfuric acid,carbonic acid, chromic acid, phosphoric acid, phosphorous acid,phosphonic acid, and combinations thereof.
 8. The method of claim 6,wherein said organic acids are selected from the group consisting ofbenzoic acid, lactic acid, acetic acid, propanoic acid, acetoaceticacid, crotonic acid, formic acid, glycolic acid, glyoxylic acid, pyruvicacid, trans-aconitic acid, fumaric acid, maleic acid, malic acid,tartaric acid, acetylenedicarboxylic acid, tetrahydrophthalic acid,mesaconic acid, phthalic acid, isophthalic acid, terephthalic acid,itaconic acid, trans-ethyleneoxidedicarboxylic acid, succinic acid,adipic acid, pimellic acid, suberic acid, azelic acid, substitutedphosphoric acid, substituted phosphorous, citric acid, hemimelliticacid, trimellitic, trimesic acid, 2carboxyethyliminodiacetic acid,nitrilotriacetic acid, phosphonic acid, substituted phosphonic acid,mellophanic acid, prehnitic acid, pyromellitic acid,2-phosphonoethyliminodiacetic acid, diethylenetetraacetic acid, andcombinations thereof.
 9. The method of claim 1, wherein said oxidizingagent is a strong nucleophile.
 10. The method of claim 9, wherein saidstrong nucleophile is an alkoxide.
 11. The method of claim 1, whereinsaid mixture is black.
 12. The method of claim 1, wherein said substrateis paper.
 13. The method of claim 12, wherein said paper is non-porouspaper.
 14. The method of claim 1, wherein said eradicable dye is atriarylmethane derivative.
 15. The method of claim 1, wherein saideradicable dye is present in said mixture in an amount at least about0.01% and up to about 40% by weight of the total weight of the mixture.16. The method of claim 15, wherein said eradicable dye is present insaid mixture in an amount at least about 0.1% and up to about 10% byweight of the total weight of the mixture.
 17. The method of claim 1,wherein said colored pigment is present in said mixture in an amount atleast about 0.01% and up to about 50% by weight of the total weight ofthe mixture.
 18. The method of claim 17, wherein said colored pigment ispresent in said mixture in an amount at least about 0.1% and up to about20% by weight of the total weight of the mixture.
 19. The method ofclaim 1, wherein said mixture further comprises a non-eradicable dye.20. The method of claim 19, wherein said non-eradicable dye is selectedfrom the group consisting of non-eradicable blue dyes, non-eradicablered dyes, non-eradicable violet dyes, non-eradicable yellow dyes,non-eradicable orange dyes, and combinations of the foregoing.
 21. Themethod of claim 1, wherein said applying said mixture comprisesdispensing said mixture from a writing instrument.
 22. The method ofclaim 1, wherein said applying said mixture comprises dispensing saidmixture from a printer cartridge.
 23. The method of claim 22, saidapplying said mixture comprises dispensing said mixture from acontinuous ink-jet printhead.
 24. The method of claim 22, said applyingsaid mixture comprises dispensing said mixture from a drop-on-demandink-jet printhead.
 25. The method of claim 24, wherein saiddrop-on-demand ink-jet printhead comprises a printhead selected from thegroup consisting of a piezoelectric ink-jet printhead, and a thermalink-jet printhead.
 26. A kit, comprising a first solution comprising amixture comprising water, a colored pigment, and an eradicable dyeselected from the group consisting of diarylmethane derivatives,triarylmethane derivatives, methine dyes, and combinations thereof; asecond solution comprising an eradicator fluid; and a third solutioncomprising an oxidizing agent.
 27. The kit of claim 26, wherein saideradicator comprises a reducing agent.
 28. The kit of claim 27, whereinsaid reducing agent is selected from the group consisting of asulfur-containing reducing agent, a basic reducing agent, andcombinations thereof.
 29. The kit of claim 28, wherein saidsulfur-containing reducing agent is selected from the group consistingof a sulfite reducing agent, a bisulfite reducing agent, a metasulfitereducing agent, a thiosulfite reducing agent, and combinations thereof.30. The kit of claim 26, wherein said oxidizing agent comprises an acid.31. The kit of claim 30, wherein said acid is selected from the groupconsisting of mineral acids, organic acids, and combinations thereof.32. The kit of claim 31, wherein said mineral acids are selected fromthe group consisting of hydrochloric acid, hydrobromic acid, hydroiodicacid, hydrofluoric acid, nitric acid, sulfuric acid, carbonic acid,chromic acid, phosphoric acid, phosphorous acid, phosphonic acid, andcombinations thereof.
 33. The kit of claim 31, wherein said organicacids are selected from the group consisting of benzoic acid, lacticacid, acetic acid, propanoic acid, acetoacetic acid, crotonic acid,formic acid, glycolic acid, glyoxylic acid, pyruvic acid, trans-aconiticacid, fumaric acid, maleic acid, malic acid, tartaric acid,acetylenedicarboxylic acid, tetrahydrophthalic acid, mesaconic acid,phthalic acid, isophthalic acid, terephthalic acid, itaconic acid,trans-ethyleneoxidedicarboxylic acid, succinic acid, adipic acid,pimellic acid, suberic acid, azelic acid, substituted phosphoric acid,substituted phosphorous, citric acid, hemimellitic acid, trimellitic,trimesic acid, 2-carboxyethyliminodiacetic acid, nitrilotriacetic acid,phosphonic acid, substituted phosphonic acid, mellophanic acid,prehnitic acid, pyromellitic acid, 2-phosphonoethyliminodiacetic acid,diethylenetetraacetic acid, and combinations thereof.
 34. The kit ofclaim 26, wherein said mixture is black.
 35. The kit of claim 26,wherein said eradicable dye is a triarylmethane derivative.
 36. The kitof claim 26, wherein said eradicable dye is present in said mixture inan amount at least about 0.01% and up to about 40% by weight of thetotal weight of the mixture.
 37. The kit of claim 36, wherein saideradicable dye is present in said mixture in an amount at least about0.1% and up to about 10% by weight of the total weight of the mixture.38. The kit of claim 26, wherein said colored pigment is present in saidmixture in an amount at least about 0.01% and up to about 50% by weightof the total weight of the mixture.
 39. The kit of claim 38, whereinsaid colored pigment is present in said mixture in an amount at leastabout 0.1% and up to about 20% by weight of the total weight of themixture.
 40. The kit of claim 26, wherein said mixture further comprisesa non-eradicable dye.
 41. The kit of claim 40, wherein saidnon-eradicable dye is selected from the group consisting ofnon-eradicable blue dyes, non-eradicable red dyes, non-eradicable violetdyes, non-eradicable yellow dyes, non-eradicable orange dyes, andcombinations of the foregoing.
 42. The kit of claim 26, wherein saidmixture further comprises a binder resin.
 43. The kit of claim 26,wherein said mixture further comprises an organic solvent.
 44. The kitof claim 26, wherein said mixture further comprises an additive selectedfrom the group consisting of pH buffers, surfactants, biocides,anti-corrosive agents, sequestering agents, anti-crusting agents,rehology control agents, binder resins, film-forming agents, andcombinations thereof.
 45. The kit of claim 26, wherein said mixture isdisposed in a writing instrument.
 46. The kit of claim 26, wherein saidmixture is disposed in a printer cartridge.
 47. The kit of claim 46,wherein said mixture is disposed in a continuous ink-jet printhead. 48.The kit of claim 46, wherein said mixture is disposed in adrop-on-demand ink-jet printhead.
 49. The kit of claim 48, wherein saiddrop-on-demand ink-jet printhead comprises a printhead selected from thegroup consisting of a piezoelectric ink-jet printhead, and a thermalink-jet printhead.